In hydraulic pumps that are driven by an electric motor, it has been common practice to provide the electric motor in one housing and the hydraulic pump in another housing, with the two housings positioned in-line. The motor and pump have their own sets of bearings and shafts that are usually engaged through internal and external splines or through flexible couplings. Such an arrangement is axially long, and necessitates the use of mounting brackets and alignment guides.
U.S. Pat. No. 4,729,717 discloses an electric-motor in-line hydraulic pump that comprises a common housing, a stationary shaft mounted in the housing, and spaced piston-type cylinder block subassemblies that rotate around and are mounted on the shaft. Each cylinder block has a plurality of circumferentially spaced pistons. The cylinder block subassemblies are positioned so that the pistons of one subassembly extend toward the other subassembly. A common yoke plate is mounted between the two cylinder blocks and bears the two groups of piston shoes, one on each of its two bearing surfaces. Each cylinder block is driven independently of and in a direction opposite to the other by an electric motor integrally mounted such that its hollow rotor houses and drives the block. All components described above are contained in one housing and operate submerged in hydraulic fluid.
U.S. application Ser. No. 07/687,173 discloses a electric-motor in-line hydraulic apparatus that comprises a housing having end members closing the housing, an electric motor stator mounted in the housing, an electric motor rotor, a shaft on which the rotor is mounted journalled in the housing, and a pump integrally formed within one or both of the end members. The shaft extends through an opening in the end member and is connected to the rotating group of the pump. Hydraulic fluid is supplied to the interior of the electric motor housing and flows through passages in the housing to the intake of the pump integral with the end member. The end member associated with the pump is formed with an enlarged chamber adjacent to the inlet of the pump that functions to reduce the flow velocity and to permit the separated air to dissolve back into solution with the hydraulic fluid, thereby reducing the operating sound level of the pump. Application Ser. No. 07/787,670 filed Nov. 4, 1991 discloses in-line electric-motor pumps of similar character in which the pump mechanism comprises a piston pump, a vane pump, a gear pump or combinations thereof.
It is a general object of the present invention to provide an integrated electric-motor and vane-type hydraulic pump that includes a double vane pump in one or both of the housing end members, with inlet and discharge passages to both pumps being disposed entirely within the associated end member. A more specific object of the present invention is to provide an integrated pump of the described character in which each double vane pump comprises a pair of vane pump cartridges sandwiched between elements that form the associated housing end member, and in which the inlet passages to both pump cartridges are disposed within the associated end member and connect the cartridges in parallel with the housing interior without requiring connections or lines external to the housing.